1. Field of the Invention
The present invention relates to a fluid apparatus which has a bellows type pump and an accumulator for reducing pulsations of the pump.
2. Description of the Prior Art
As a pump for circulating and transporting chemical liquid in various processes such as washing of surfaces of ICs or liquid crystal display devices in a semiconductor producing apparatus, used is a bellows type pump in which no particles are generated as a result of the pumping operation (for example, Japanese Patent Application Laying-Open No. 3-179184). In a pump of this kind, pulsations are produced by reciprocal motion due to extension and contraction of the bellows. In order to reduce the pulsations, therefore, also an accumulator is used (for example, Japanese Patent Application Laying-Open No. 10-196521).
In such a fluid apparatus having a bellows, in the case where abrasive liquid containing slurry such as silica is used as a polishing solution for Chemical Mechanical Polishing (CMP) of a semiconductor wafer, a hard disk which is to be incorporated into a computer, and the like, for example, there arises the following problem.
Namely, in the pump or the accumulator, the bellows which is extendingly and contractingly deformable in the axial direction is placed in the pump body or the accumulator body. In the case where liquid containing a material such as slurry which sediments is used, therefore, the sedimenting material easily collects and sets in an extending and contracting portion of the bellows, thereby causing the bellows to be broken.
A suction port and a discharge port for liquid are disposed in the pump, and a suction check valve and a discharge check valve are disposed in the suction port and the discharge port, respectively. Therefore, the pump cannot be easily made compact. Moreover, the accumulator is connected to the downstream side of the discharge port of the pump via a connecting pipe or the like, so that a pressure loss due to vibrations of the connecting pipe and friction with the inner face of the pipe during passage through the pipe is produced in liquid discharged from the discharge check valve. Therefore, the pressure of liquid flowing into the accumulator is lower than that of liquid discharged from the pump. As a result, the response performance of the accumulator cannot be easily improved, and gas components and the like entering the accumulator cannot be easily discharged with being embraced by the liquid.